[sebhc] Diskette Drives

Lee Hart leeahart at earthlink.net
Sat Jun 17 22:47:32 CDT 2006

Barry Watzman wrote:
> Diskettes created on the Siemens drives cannot be read by an IBM PC drive
> and vice versa."
> That absolutely, positively should not be the case.  Something is wrong if
> it is.

I agree. I have installed PC 5.25" drives in H8s and H89 many times, and
it always worked (eventually). The main challenge is that PCs jumper
their drives differently than the Heathkits.

The big difference is that PCs jumper all drives to be DS2; they cut and
twist the cable to allow two drives on one cable with identical Drive
Select jumpering. Heathkits cable all drives in parallel, and use the
drive's four Drive Select jumpers (DS0-DS3 or DS1-DS4, depending on the

The second difference is that the PCs don't use the head load solenoid
(if the drive is so equipped; Tandons don't have it). Heath does use it;
so you have to jumper the drive to load the head when selected. The
jumper is labelled something like "HS".

The final difference is that PCs only turn on the motor of the one drive
that is selected. The PC software then has to wait for that drive to
come up to speed. Heathkits start the motors in all drives together, so
they don't have to wait for the drive to come up to speed. So, if the PC
drive's motor is slow to come up to speed, it will cause problems in a
Heathkit (BDOS errors in CP/M etc.). Thus, you have to jumper the PC
drive so its motor is controlled by the Motor line, not by the Select

I've found that my H89s can use just about *any* drive, once I've
figured out the jumpers for it!
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in    --    Leonard Cohen
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net
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